Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $72.61   4.761%   $76.067   $76.07   $76.05   $76.10  
  Purchase #2 $64.79   13.346%   $73.4369   $73.44   $73.45   $73.40  
  Purchase #3 $199.96   5.351%   $210.6599   $210.66   $210.65   $210.70  
  Purchase #4 $28.91   4.312%   $30.1566   $30.16   $30.15   $30.20  
  Purchase #5 $8.61   4.437%   $8.992   $8.99   $9.00   $9.00  
  Purchase #6 $222.33   6.280%   $236.2923   $236.29   $236.30   $236.30  
  Purchase #7 $75.75   8.204%   $81.9645   $81.96   $81.95   $82.00  
  7 purchase totals = $672.96       $717.5692   $717.57   $717.55   $717.70